The distribution of plasmids that carry virulence and resistance genes in Staphylococcus aureus is lineage associated.

BACKGROUND: Staphylococcus aureus is major human and animal pathogen. Plasmids often carry resistance genes and virulence genes that can disseminate through S. aureus populations by horizontal gene transfer (HGT) mechanisms. Sequences of S. aureus plasmids in the public domain and data from multi-strain microarrays were analysed to investigate (i) the distribution of resistance genes and virulence genes on S. aureus plasmids, and (ii) the distribution of plasmids between S. aureus lineages. RESULTS: A total of 21 plasmid rep gene families, of which 13 were novel to this study, were characterised using a previously proposed classification system. 243 sequenced plasmids were assigned to 39 plasmid groups that each possessed a unique combination of rep genes. We show some resistance genes (including ermC and cat) and virulence genes (including entA, entG, entJ, entP) were associated with specific plasmid groups suggesting there are genetic pressures preventing recombination of these genes into novel plasmid groups. Whole genome microarray analysis revealed that plasmid rep, resistance and virulence genes were associated with S. aureus lineages, suggesting restriction-modification (RM) barriers to HGT of plasmids between strains exist. Conjugation transfer (tra) complex genes were rare. CONCLUSION: This study argues that genetic pressures are restraining the spread of resistance and virulence genes amongst S. aureus plasmids, and amongst S. aureus populations, delaying the emergence of fully virulent and resistant strains

Staphylococcus aureus temperate bacteriophage: carriage and horizontal gene transfer is lineage associated.

Staphylococcus aureus is a major cause of human and animal infections. Bacteriophage are a class of mobile genetic element (MGE) that carry virulence genes and disseminate them horizontally, including Panton-Valentine leukocidin (PVL), the immune evasion cluster (IEC) associated with human specificity, and enterotoxin A the major toxin associated with food poisoning. S. aureus isolates group into major clonal complex (CC) lineages that largely evolve independently due to possession of different restriction-modification (RM) systems. We aimed to better understand the horizontal and vertical transmission dynamics of virulence and resistance genes by bacteriophage by using (i) bioinformatic approaches to analyze bacteriophage genomes from the first 79 sequenced S. aureus isolates and (ii) S. aureus microarrays to analyze the distribution of bacteriophage and virulence genes in S. aureus isolates from a broader range of lineages. The distribution of eight bacteriophage families was highly variable but lineage associated. Nevertheless, there was evidence of frequent acquisition and loss and not just vertical transmission. Most bacteriophage genes were dispensable, and extensive mosaicism was seen. Surprisingly, virulence genes were tightly associated with specific phage families. This data suggests S. aureus bacteriophage evolve rapidly, and the horizontal gene transfer (HGT) of virulence genes encoded by bacteriophage is restricted by bacteriophage family and the lineage of the host bacterium, delaying the evolution of fully resistant and virulent strains

Shuffling of mobile genetic elements (MGEs) in successful healthcare-associated MRSA (HA-MRSA).

Methicillin-resistant Staphylococcus aureus (MRSA) CC22 SCCmecIV is a successful hospital-associated (HA-) MRSA, widespread throughout the world, and now the dominant clone in UK hospitals. We have recently shown that MRSA CC22 is a particularly fit clone, and it rose to dominance in a UK hospital at the same time as it began acquiring an increased range of antibiotic resistances. These resistances were not accumulated by individual CC22 isolates, but appear to shuffle frequently between isolates of the MRSA CC22 population. Resistances are often encoded on mobile genetic elements (MGEs) that include plasmids, transposons, bacteriophage and S. aureus pathogenicity islands (SaPIs). Using multi-strain whole genome microarrays, we show that there is enormous diversity of MGE carried within a MRSA CC22 SCCmecIV population, even among isolates from the same hospital and time period. MGE profiles were so variable that they could be used to track the spread of variant isolates within the hospital. We exploited this to show that the majority of patients colonised with MRSA at hospital admission that subsequently became infected were infected with their own colonising isolate. Our studies reveal MGE spread, stability, selection and clonal adaptation to the healthcare setting may be key to the success of HA-MRSA clones, presumably by allowing rapid adaptation to antibiotic exposure and new hosts

Analysis of Escherichia coli K1 virulence genes by transposon-directed sequencing

Transposon-directed insertion site sequencing (TraDIS) combines random transposon mutagenesis and massively parallel sequencing to shed light on bacterial gene function on a genome-wide scale and in a high-throughput manner. The technique has proven to be successful in the determination of the fitness contribution of every gene under specific conditions both in vitro and in vivo. In this contribution, we describe the procedure used for the identification of Escherichia coli K1 genes essential for in vitro growth, survival in pooled human serum and gastrointestinal colonisation in a rodent model of neonatal invasive infection. TraDIS has broad application for systems-level analysis of a wide range of pathogenic, commensular and saprophytic bacteria

Extensive horizontal gene transfer during Staphylococcus aureus co-colonization in vivo.

Staphylococcus aureus is a commensal and major pathogen of humans and animals. Comparative genomics of S. aureus populations suggests that colonization of different host species is associated with carriage of mobile genetic elements (MGE), particularly bacteriophages and plasmids capable of encoding virulence, resistance, and immune evasion pathways. Antimicrobial-resistant S. aureus of livestock are a potential zoonotic threat to human health if they adapt to colonize humans efficiently. We utilized the technique of experimental evolution and co-colonized gnotobiotic piglets with both human- and pig-associated variants of the lineage clonal complex 398, and investigated growth and genetic changes over 16 days using whole genome sequencing. The human isolate survived co-colonization on piglets more efficiently than in vitro. During co-colonization, transfer of MGE from the pig to the human isolate was detected within 4 h. Extensive and repeated transfer of two bacteriophages and three plasmids resulted in colonization with isolates carrying a wide variety of mobilomes. Whole genome sequencing of progeny bacteria revealed no acquisition of core genome polymorphisms, highlighting the importance of MGE. Staphylococcus aureus bacteriophage recombination and integration into novel sites was detected experimentally for the first time. During colonization, clones coexisted and diversified rather than a single variant dominating. Unexpectedly, each piglet carried unique populations of bacterial variants, suggesting limited transmission of bacteria between piglets once colonized. Our data show that horizontal gene transfer occurs at very high frequency in vivo and significantly higher than that detectable in vitro

Comparative host specificity of human- and pig- associated Staphylococcus aureus clonal lineages.

Bacterial adhesion is a crucial step in colonization of the skin. In this study, we investigated the differential adherence to human and pig corneocytes of six Staphylococcus aureus strains belonging to three human-associated [ST8 (CC8), ST22 (CC22) and ST36(CC30)] and two pig-associated [ST398 (CC398) and ST433(CC30)] clonal lineages, and their colonization potential in the pig host was assessed by in vivo competition experiments. Corneocytes were collected from 11 humans and 21 pigs using D-squame® adhesive discs, and bacterial adherence to corneocytes was quantified by a standardized light microscopy assay. A previously described porcine colonization model was used to assess the potential of the six strains to colonize the pig host. Three pregnant, S. aureus-free sows were inoculated intravaginally shortly before farrowing with different strain mixes [mix 1) human and porcine ST398; mix 2) human ST36 and porcine ST433; and mix 3) human ST8, ST22, ST36 and porcine ST398] and the ability of individual strains to colonize the nasal cavity of newborn piglets was evaluated for 28 days after birth by strain-specific antibiotic selective culture. In the corneocyte assay, the pig-associated ST433 strain and the human-associated ST22 and ST36 strains showed significantly greater adhesion to porcine and human corneocytes, respectively (p<0.0001). In contrast, ST8 and ST398 did not display preferential host binding patterns. In the in vivo competition experiment, ST8 was a better colonizer compared to ST22, ST36, and ST433 prevailed over ST36 in colonizing the newborn piglets. These results are partly in agreement with previous genetic and epidemiological studies indicating the host specificity of ST22, ST36 and ST433 and the broad-host range of ST398. However, our in vitro and in vivo experiments revealed an unexpected ability of ST8 to adhere to porcine corneocytes and persist in the nasal cavity of pigs

The views of managers and recruitment specialists in relation to migrants' opportunities in recruitment and selection processes in Australia

Australia’s population is one of the world’s most culturally and linguistically diverse. With declining fertility rates, the overall intake of immigrants will continue to increase with the proportion of Asian immigrants predicted to rise significantly over the next 50 years. Despite many of these immigrants holding recognised qualifications and previous work experience, a high proportion are faced with unemployment or employment in positions, which are not commensurate with their knowledge and abilities. This paper which examines the views of managers and recruitment specialists is part of a larger study investigating the experiences of South-east Asian migrants in recruitment and selection in Australia. Surveys were administered to Master of Business Administration students who are currently employed in management positions. Due to the increasingly popular trend of outsourcing HR activities, 10 Recruitment Consultants were interviewed with questions based upon the managers’ questionnaire. The responses to questions relating to the difficulties that migrants are faced with in recruitment and selection, and recommendations as to what migrants may do regarding behaviour and training, were analysed. Overall, communication and cultural issues were seen as central to the difficulties experienced by migrants in recruitment and selection processes and therefore carved the basis upon which recommendations were formed. The findings of this study have implications for human resource professionals and employment support agencies who are actively involved with recruitment and selection in general, or who specialise in assisting migrants with job seeking

Preferences in recruitment and selection in a sample of Australian organisations

The diversity of the Australian workforce has increased over the last 25 years, particularly with the increase in the number of migrants from South-east Asia. Despite the knowledge, skill and expertise that many of these immigrants possess prior to migrating, a high proportion of immigrants experience significant difficulties obtaining employment commensurate with their abilities. This paper is an exploratory study of the preferences of managers, recruitment specialists and migrants regarding recruitment and selection practices in selected Australian cities. Surprisingly, the findings revealed similarities between the three groups (managers, migrants and recruitment consultants). Thus, this study adds to the debate about the impact of cross-cultural expectations in recruitment and selection in Australian organisations

The role of communication in recruitment and selection in Australia

In Australia, unemployment and under-employment continue to be significant issues experienced bymigrants from non-English-speaking backgrounds (NESB). Despite these immigrants having relevant qualifications, skills, and work experience, a high proportion have difficulties in obtaining employment in Australian organisations. Communication or language proficiency has been identified as one of the primary causal factors. Moreover, studies have identified the importance of communication as a key competency sought by managers and recruiters in all job applicants. Given the importance of making employment decisions more objective and measurable to meet anti-discrimination requirements, this study examines the perceptions of managers and recruitment specialists about the communication skills that are essential for successful recruitment and selection. Subsequently, areas for inteNention are highlighted

Midwifery continuity : the use of social media

Background Continuity models of midwifery care improve women’s experiences of care and clinical outcomes, but organisationally driven working practices do not facilitate a continuity model and the midwifery care received by most women is fragmented (Sandall et al., 2016, NHS England, 2016). Little is known about the potential for continuity of midwifery care to be achieved using an electronic platform. This paper examines the experiences of women accessing known midwives through a social media platform and their experiences and perception of continuity of care. Methods The study forms part of a larger research project aiming to increase understanding about online social learning within professionally moderated social media based communities. This paper reports specifically the concept of midwifery continuity within the online communities. Two secret Facebook groups consisting of 31 mothers and 4 midwife moderators were created (17 mothers &amp; 2 midwives / 14 mothers &amp; 2 midwives). Primary data included 8 online and face to face focus groups, conducted at approximately 10 week intervals, and 28 individual one to one interviews with members of the online community within six weeks of giving birth. Data analysis A thematic analysis using a priori themes was undertaken. This involved coding data which evidenced relational, informational and management continuity across the entire dataset (28 interviews and 8 focus groups). The analysis was undertaken broadly following the six stages described by Braun and Clarke (2006). Findings Relational and informational continuity were identified across the data. Relational continuity was evident for both the participants and the midwife moderators; informational continuity was described by the participants. Management continuity was not identified. Continuity through social media use was valued by both the mothers and the midwives. Conclusion Information and relational continuity needs of women can be met using professionally moderated, social media based groups. They may provide an alternative means of facilitating the continuity that is so often lacking in traditional models of care